


The Enemy Of My Enemy...Or Something Like That

by Kestrealbird



Category: Fate/stay night & Related Fandoms
Genre: AU? Maybe? Idk, Diarmuid gives approximately negative fucks in this, Gen, Humor, M/M, Pre-Relationship, Vague setting, normally Cu is the horny one but Diar took over this time oops, not porn but it was close, the C-word is dropped exactly once in this, the OC is just a daughter...protect her..., there is implied past abuse in this fic so be warned, this is mostly set-up for something larger I will never expand upon
Language: English
Status: Completed
Published: 2021-02-03
Updated: 2021-02-03
Packaged: 2021-03-15 00:13:14
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,910
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29180055
Author URL: https://archiveofourown.org/users/Kestrealbird/pseuds/Kestrealbird
Summary: “You could’ve attacked her,” Lancer says, accusing. “Why didn’t you?”Because he’s not stupid enough to fly for someones throat when he knows nothing about Lancer’s abilities. Because she’s young and innocent and reminds him far too much of his friend in their younger years. Because his own Master would want information. Because he’s a soft cunt even if he’ll never say it.He could say any of the above and they would all be true but what he settles for is a vague, “wasn’t worth it to try.”
Relationships: Cú Chulainn | Lancer/Diarmuid Ua Duibhne | Lancer
Comments: 8
Kudos: 22





	The Enemy Of My Enemy...Or Something Like That

**Author's Note:**

> There's some nods to the mythos in here that will be explained in my end notes but I just wanted to say: yo 2021 what the fuck is up with the DiarCu lately I just wanted to vibe in peace. Also this isn't super important to the fic but it's important to me so here's a reminder that I write Diarmuid as trans-gay so even tho that doesn't come up here, he is. Always

The war itself is senseless. Inane. One could argue that all wars are pointless - just bloodshed amongst bloodshed, seemingly never-ending. Once you’ve been in as many wars as Diarmuid has, though, you start to place them in a tier list, a self-made ranking. This one is, to date, the most ridiculous of the lot so far - Servant or not, he has enough self-respect to scoff at the Mages and their obsession with immortality. 

He can’t say for sure whether The Root  _ would  _ ever give them such a thing, but he  _ can  _ say that a long-lived life is not nearly as gratifying as they would think; it is, in his own experience, more  _ lonely  _ than anything. He’s wise enough to know that expressing these views outloud is probably a terrible idea, but just dumb enough that he does it anyway, which is possibly why he became Public Enemy Number One so damn quickly.

This is also  _ undoubtedly  _ the reason he finds himself waking up, hands bound behind the pillar at his back, in a dusty cell with rotting beams of wood trying valiantly to hold up the ceiling, and crows cawing ominously from the window. Props to whichever Mage designed this place - the atmosphere is quite gothic and, if he were human, Diarmuid might even say it was ‘creepy.’ 

But he isn’t human, so he finds it more ‘adorable’ than anything. Reminds him of the jails back in Ireland. Feels just a little bit like home.

His captors haven’t bothered to tie his feet or legs, which is very stupid of them, but he’s impressed that they managed to get him here at all, so he sits cross-legged and pretends that he hasn’t already figured out how to undo the knots of the rope on his wrists.

May as well try to learn something while he’s here and not go back to his - he grimaces -  _ Master  _ empty-handed.

There are six people in the room with him, whispering and muttering amongst themselves, none of them equipped enough to keep him here -

_ Ah. Except that one. _

None of the Mages seemed to have noticed that he’s awake quite yet - proof of their arrogance, perhaps, or maybe just inexperience - but Diarmuid spies another Servant near the door, arms crossed over his chest, head bowed, a spear of bright green leaning against the wall beside him. His clothing is modern - a simple white shirt and some black leathers - so, at first glance, it’s difficult to place where he’s from, but he shifts in place, and the light from the window catches the tightness of his shirt and Diarmuid’s mouth temporarily dries out at the sight of muscle underneath.

A large, red tattoo takes up his right side, disappearing beneath his belt and reaching up to his shoulder. It’s an old design. Celtic. Diarmuid’s head still throbs with a dull ache, more irritating than painful, and it’s enough to distract him from trying to puzzle out the design. He feels as though he’s seen it before, somewhere. Feels like he should  _ know  _ the region it’s from.

The fact that this Servant has long hair cascading over his shoulder is definitely  _ not  _ helping matters. Curse his weakness for handsome men.

Finally, one of the Mages notices he’s awake, and cautiously approaches him. She looks young. Younger than most. It’s always so hard to tell which humans are adults and which ones aren’t, but Diarmuid’s pretty certain that this one is more girl than woman, a jagged scar bisecting her face and old burns on her hands that speak of spells gone awry. 

She grins at Diarmuid, and it comes out more like a wince. 

“You were a right pain to get,” she informs him.

“I was minding my own business,” Diarmuid drawls. “Until someone hit me over the head, I’m guessing.”

She blinks, hesitating as though she’s  _ concerned  _ for him or something, gaze flickering over him as she scans for an injury that’s long since healed. Inexperience soaks into her eyes like the warmth of summer, an orange haze. She reminds him of a friend from days long past, and the thought  _ almost  _ makes him smile. “How did you…?”

“Well, the pounding headache is pretty hard to miss.” The other Servant chuckles, low and rough.  _ Fuck. _ Diarmuid swallows and nods his head towards the ropes behind him. “Is  _ this  _ really necessary?”

Her eyes glance back to the Servant, lip caught between her teeth. She’s trying very hard to look more confident than she is, and Diarmuid feels his heart soften. “We had to wait a long time to get you unawares,” she says carefully. “It’d be terrible for us if you managed to escape after all that trouble.”

Smart of her, he thinks with a surge of distant pride.  _ When  _ he gets out - not if;  _ when  _ \- he’s going to be a lot harder to jump again. He’ll keep to crowded streets, for one, and have his dogs nearby to keep their noses out for trouble.

He has no idea why these people want him alive, and he’s not particularly interested in finding out, but his Master’s voice will go that high screechy pitch if he doesn’t. The only reason he hasn’t gotten rid of them yet is because they were paranoid enough to have him promise not to personally harm them, and he is nothing if not bound by such contracts.

“Can I at least ask why I’m here?”  _ And not dead, _ he doesn’t say, though it lingers in the air regardless. The other Mages in the room are silent, and the girl opens her mouth to answer, but the Servant steps forward to stop her, a frown tugging his lips downwards - and wow but his eyes are bright as torchlight, redder than the jewels his Aunt wears on her fingers, his skin a soft tan, and Diarmuid’s eyes linger at the bareness of his throat.

It’d be so easy to sink his teeth into it; feel the blood on his tongue and leave a bruise in his wake. Shit. If the sight of this guy is enough to stall his thoughts, then there might not be much hope of him leaving after all. It’s been a while since he’s messed around with someone, and this War has left him frustrated in more ways than one, so sue him for being...easily distracted, when in the presence of a guy who is, unfortunately, checking off a lot of marks on his ‘my type’ list.

Diarmuid would like to think that he would never fall in love at first sight - that he was above such disgusting drivel - but the man before him has such splendor about him that he can hardly look away for long, captivated despite his best efforts to the contrary. He reigns in his sudden desire before he can do something mortifying like try to get close enough that he can touch the light bleeding over the Servant’s skin, a faint red hue at the edges.

The man’s eyes settle on his own and Diarmuid’s heart does an embarrassing stutter-stop in his chest, his stomach twisting with low, simmering heat. He’s normally much colder than this.

“Sorry Lancer,” the girl mumbles, ducking her head even as Lancer - he should’ve guessed as much from the spear, but attraction based idiocy has taken the place of rationality - ruffles her hair.

Lancer doesn’t look back at the other Mages in the room when he narrows his eyes and says, “leave us.” 

He’d be jealous that Lancer has so much control here if the depth of his vocal tone wasn’t so damn compelling. Still, Diarmuid is nothing if not an asshole, so he leans as far to the side as he can to give the retreating Mages a bright, overly polite smile. It’s the same smile his friend used to carry when he was manipulating local Lords and Ladies; the kind that closes your eyes and projects sincerity as you make passive threats veiled under casual conversation.

Naturally, it makes them shudder and leave the room with a little more haste. A few moments after the door closes, once it’s apparent that nobody is listening in, Lancer squats in front of him, arms over his knees, a mixed expression of intrigue and confusion. He cocks a brow upwards, giving a pointed look to his arms, and Diarmuid sighs with a smile. There’s no point standing up for this, so he doesn’t, lifting his hands in a gesture of surrender as he lets the rope that was binding them fall to the floor behind him. 

Lancer’s Master jerks backwards, eyes wide as she realizes just how close she came to getting stabbed had her Servant not stepped forward when he did. Diarmuid didn’t actually plan on stabbing her, of course, but another Servant might’ve and it’d be a shame for a life as innocent as her own to be taken so quickly. 

“You could’ve attacked her,” Lancer says, accusing. His accent is an odd one - a strange mixture of Northern Irish and Scottish. Accents have never been his forte but something about it begs familiarity and if he doesn’t figure out who this guy is soon he may just go mad.

He shrugs. “I could’ve.”

“Why didn’t you?”

Because he’s not stupid enough to fly for someones throat when he knows nothing about Lancer’s abilities. Because she’s young and innocent and reminds him far too much of his friend in their younger years. Because his own Master would want information. Because he’s a soft cunt even if he’ll never say it. 

He could say any of the above and they would all be true but what he settles for is a vague, “wasn’t worth it to try.” 

Lancer smirks, an amused gleam in his eyes. Even with the gap between them, Diarmuid can feel Lancer’s warmth, less like a woolen blanket and more like a heavy fur cloak. He wants, so very badly, to reach out and curl himself against it - he’s never felt warmth before. It’s thrilling and he shivers, biting back a noise of complaint when Lancer moves away from him. Selfish bastard should share it.

Part of the noise slips out anyway and even though he manages to cover it as an exaggerated groan of discomfort, he only succeeds in lying to the young miss and he curses Lancer for being more observant. “Will you stab me if I stand up?” he asks, suddenly desperate to stretch his limbs so he doesn’t have to think too hard about lingering heat and tanned skin beneath his teeth and the way Lancer’s smile quirks up to the side.

“No,” the miss says, to which Lancer rolls his eyes. She sounds a lot more sure of herself now that they’re alone, just the three of them. Still a girl - innocent, inexperienced - yet bolder. Braver. 

“Oh?”

“...do you intend to stab  _ us? _ ”

“Us” she says, as if herself and Lancer are a unit instead of temporary accomplices. He shrugs again, shoving his hands into his pockets as he pushes himself up with leg strength alone. So maybe he’s showing off a little, just to feel out his chances with Lancer, to see if the instant attraction is mutual and - yeah okay he can  _ feel  _ the way Lancer’s eyes slowly track their way up his legs before settling on his thighs. They’re very nice thighs, he’s aware, and the attention makes him preen.

“Not particularly,” Diarmuid tells her, leaning back against the pillar as casually as he can manage, crossing one leg in front of the other. “So what’s so special about you?”

“Pardon?”

“You had Lancer bring me here I assume? I doubt one of your... _ compatriots _ would’ve managed it, and there must be a reason you’re willing to risk your own safety by keeping me alive.” She rears back as if struck and Lancer’s posture straightens. Diarmuid smirks. “Don't worry,” he assures her, “I’m not interested in knowing that last bit. Just wanted to see how you’d react is all.”

“Everyone kind of hates you right now,” Lancer says, which,  _ ouch, _ but also? Fair enough. “The Miss wants to propose a treaty to you.” Now, isn’t that interesting? A treaty with someone who has almost every target on his back over a treaty with someone whose safer? Either she is truly  _ desperate  _ for help or -

He looks back to the burns on her hands, thinks of how jumpy she is, how unsure, and suddenly those burns look less like accidents and more like fear. His face goes purposefully neutral as he considers the implications of this; she must’ve seen or heard about him hanging around the younger generations, keeping a careful eye on them and leading all of his fights away from their homes. It’s no secret once you know what to look for.

“So, what? I help you and you hide me in a basement so I don’t get sniped for being mouthy?”

“I - not exactly,” the Miss says quietly, apologetic and oh so earnest, so hopeful.

It would be all too easy to get information out of her, even with Lancer here. Her tells are too obvious, her eagerness too loud. Her own people clearly have no idea what she’s planning, but whether that’s because of herself or Lancer is debatable. Damn his soft heart but he can't do that to her, not when he sees so much of - he shakes his head, huff's a breath and says, “if you’d permit me a request, I’d like to speak with Lancer in private first.”

Lancer stills and the Miss blinks, mouth forming a small ‘o’ as she looks back and forth between them. “It’s nothing terrible,” he says. Then, teasingly, “it’s a grown up thing.”

She pouts, “I’m not a child,” but looks to Lancer for guidance anyway. “Alright,” Lancer says slowly, cautiously, and waits until his Master has left the room before all of his undivided attention snaps to Diarmuid and it’s  _ exhilarating.  _ “I’m not telling you her name.”

“I refuse to work with someone who doesn’t have a name.”

Lancer snorts without humour. “Call her whatever you like, then, if it would make you feel better.”

“Are you sure? I might end up calling her something like ‘Pancake’ or ‘Karen.’”

“...point taken.” His steps are slow, measured, and Diarmuid tracks each one with his eyes, lifting his head as Lancer walks a careful circle around him, stopping only when they’re face to face again. It’s less of a threat and more of an assessment, trying to see if he’s worth all the trouble. “No name,” Lancer repeats, “until I know your answer.”

Damn. Just his luck that he’d end up negotiating with someone who actually knows what they’re doing. He’d hoped that Lancer would’ve been easier to manipulate; any guilt he felt towards the Miss didn’t extend to her Servant, and he should’ve felt more annoyed by that. Instead he simply mentally ticks off another box on his list. 

“Alright,” Diarmuid concedes at last with a wave of his hand. “Go on then. Lay your terms and conditions.” 

“That’s not an agreement.”

“Fuck you, man, can’t you make it easy for me?”

Lancer smirks. “No.”

Fucker.

He sighs, deflating. “Fine then. Why me, out of everyone?”

“You don’t hurt kids,” Lancer says simply. It’s what he’d already guessed, of course, but it riles him regardless and he visibly bristles, clicking his tongue to stop himself from snarling. “She doesn’t care about the war,” Lancer says before he can ask. 

“Revenge, then?”

A shrug. Dismissive. “No.” Lancer’s voice goes quiet, impossibly soft. “She just wants to live, is all.”

His head hits the pillar with a quiet ‘thunk.’ “Shit,” he breathes, getting a hummed agreement. What can he say to that, except ‘sure, yeah, whatever you want?’ What can he say except ‘did you kill them for the pain they caused her, or do I have to do it myself?’ 

“Do something for me first,” he says, “and if you manage it we’ll talk about specifics. With her in the room, of course, so she knows what’s going on.”

Lancer cocks his head, considering. Weighing his options. Diarmuid has no idea if Lancer agrees with the Miss or not but he’s at least willing to go along with her plans - if he wasn’t then Diarmuid has no illusions about whether he’d still be alive or not. “Depends,” Lancer states, “on what you want me to do.”

Diarmuid’s Master was a coward of a Mage, voice too high pitched and screechy, orders too demanding - his clothes nothing more than a curtain to hide their hubris, their conceit, their sense of self-importance. They’d made him promise not to hurt them, kill them...but the devil in the details was that he had never promised to  _ protect  _ them. 

“Well,” he muses, “I’m going to need some measure of freedom to help her. Can’t do much if I’m still bound to someone else, now can I?”

Lancer offers no judgement, just a simple, “aah,” of understanding and a nod. “A deal, then?”

“I don’t work with people who have no names,” Diarmuid reminds him, just to test his own luck.

“Tell you mine if you tell me yours,” Lancer jokes, probably not expecting him to agree that it’s a fair exchange.

He holds out a hand. “Diarmuid.”

“...ua Duibhne?” 

“Are there any others?”

Lancer laughs, shakes his head, and grips Diarmuid’s hand firmly. “Cú Chulainn. From Ulster, of course.”

Oh.

_ Oh fuck. _

**Author's Note:**

> Mythos nods explained! The red haze around Cu's skin is a nod to the fact that in his legends his body was so hot that it glowed red. Similarly, the reason why Diarmuid can't look away from him for long is because Cu was canonically the sort of person who just...drew attention simply by existing. Also I thought it'd be a fun bit of irony for the guy with a love curse to get captivated so easily lol. Diarmuid's protectiveness of children is _mostly _because he helped Fionn raise his own kids so he has a bit of a soft spot__
> 
> __Reasons why they don't know eachother immediately: Fate threw this out completely but in his legends, Diarmuid kept his love spot covered by his hair, which is what's happening here. Without said love spot he could be pretty much anyone. Cu has a lot of conflicting accounts in his legends about his appearance; some stories say he has dark eye and a brooding expression, whereas others describe him as having strong features with tri-coloured hair and seven eyes and fingers. His accent being a mix of Scottish and Irish is my own HC about him picking up Scathach's accent after living with her for so long_ _
> 
> __Diarmuid's "oh fuck" at the end is bc my other big HC is that he's had a biiiit of a crush on Cu Chulainn since he was a boy, the same way we get crushes on famous celebrities. He's not a fanboy, exactly, but he is dying a bit on the inside now. Whoops_ _


End file.
